"Our study is the first to examine whether learning a second language impacts cognitive performance later in life while controlling for childhood intelligence," said lead author Thomas Bak from University of Edinburgh.

However, researchers are unable to clearly pinpoint what helps with cognitive performance, whether it's that learning a second language helps or if people with high cognitive performance are more likely to know more than one language.

"The crucial question is whether people improve their cognitive functions through learning new languages or whether those with better baseline cognitive functions are more likely to become bilingual," said Bak, who is also a lecturer at the University of Edinburgh.

The study was based on data from the Lothian Birth Cohort 1936, which involved 835 native English speakers who were born and resided in Scotland in the UK. Of the 835 participants tested, 262 were able to speak two or more languages. Of these, 195 learned a second language before the age of 18 (19 before the age of 11) while 65 learned a second language after the age 18.

This is not the first study of its kind. Another study of bilingualism in 2013 found that bilingual patients suffer dementia onset an average of 4.5 years later than those who speak only one language. A significant difference in age at onset was found across Alzheimer's disease dementia as well as other kinds of dementia.